Supercharging combustion engines

ABSTRACT

Method and Apparatus for supercharging the cylinder, wherein additional air is compressed in two stages and only delivered to the cylinder in bulk during the suction stage of the working cycle. In the expansion stage the compressed air is diverted to the other cylinders and only a portion of the compressed air is delivered to the cylinder and only at the end of the expansion stroke.

United States mm 1191 Richter Feb. 5, 1974 SUPERCHARGING COMBUSTIONENGINES [75] Inventor: Antonin Richter, Prague,

Czechoslovakia [73 Assignee: Ustav pro vyzkurn Motorovych Vozidel,Praha, Czechoslovakia [22] Filed: June 20, 1972 [21] Appl. No.: 264,462

[30] Foreign Application Priority Data July 2, 1971 Czechoslovakia4880/71 [52] US. Cl. 123/71 R, [23/75 CC, 123/75 RC [51] Int. Cl. F02b33/14 [58] Field of Search 123/75 CC, 75 RC, 20

[56] References Cited UNITED STATES PATENTS l,297,248 3/1919 Ricardo123/75 RC 2,110,754 3/1938 Alston 123/75 CC 1,219,458 3/1917 Herbert 12375 cc FOREIGN PATENTS OR APPLICATIONS 411,017 6/1945 Italy 123/75 ccPrimary Examiner-Laurence M. Goodridge Attorney, Agent, or FirmMurraySchaffer [5 7 ABSTRACT Method and Apparatus for supercharging thecylinder, wherein additional air is compressed in two stages and onlydelivered to the cylinder in bulk during the suction stage of theworking cycle. In the expansion stage the compressed air is diverted tothe other cylinders and only a portion of the compressed air isdelivered to the cylinder and only at the end of the expansion stroke.

7 Claims, 7 Drawing Figures SUPERCHARGING COMBUSTION ENGINES BACKGROUNDOF INVENTION The invention relates to a method of two-stage compressionof additional air for supercharging internal combustion engines having adiffernential piston. The invention also relates to a device forcarrying out the method.

Known methods of supercharging four-stroke combustion engines by meansof a differential piston are characterized by an annular chamberprovided below the piston in addition to the normal working chamberabove it. Additionally, air is admitted to the annulus where it iscompressed during the downward strokes of the piston. This additionalair of an increased pressure is driven from the annulus below the pistonto the working chamber above the piston when the piston is in its bottomdead centre twice per working cycle through ducts located in the block.The cylinder becomes supercharged at the end of the suction stroke, andscavenged at the end of the expansion stroke.

An advantage of this scavenging is the effective neutralization ofenginge exhausts directly at the place of their origin by creatingadditional oxidation of incompletely burnt components. But there is herealso a disadvantage in the fact that neutralization requires anexcessive supply of additional air exceeding the actual requirement.This is naturally not without an adverse effect on the operationaleconomy and the life of the engine. This is due to the fact that theeffective amount of scavenging air increases the aggressiveness of hotgases having a high oxide content which reduces the engine life byattacking the metal.

It is therefore an object of the invention to reduce engine scavengingto the unavoidable minimum, and to transfer the amount of pressurizedair thus obtained in the annular space of the differential piston duringits expansion stroke for the benefit of engine supercharging bydischarging this pressurized air to the cylinder during the suctionstroke.

It is another object of the invention to increase the efficiency andpower ofinternal combustion engines by providing improved superchargingmeans.

These objects, as well as others, will be seen from the followingdisclosure.

SUMMARY OF INVENTION According to the present invention, the additionalair employed for supercharging the cylinder, is compressed in two stagesand only delivered to the cylinder in bulk during the suction stage ofthe working cycle. In the expansion stage the compressed air is divertedto the other cylinders and only a portion of the compressed air isdelivered to the cylinder and only at the 'end of the expansion stroke.This permits efficient oxidation of the non-combusted products but notdelivery of excess air.

More specifically, the method of the present invention comprises the useof a cylinder and piston formed to have a lower and upper chamber, andthe steps of admitting air into the lower chamber on the upstroke of thepiston and discharging compressed air on the downstroke, air beingadmitted at least twice ineach cycle, once from atmosphere or thecrankcase, and once from the discharged compressed air of the othercylinders. The air is discharged, in part, to the same cylinder tocharge it during the suction or intake stroke and during the nextdownward stroke to the associated cylinders, and later to the samecylinder for use in oxidation during the expansion stroke.

According to the present invention, the method is carried out withsimple modification of the engine, provides apparatus comprising ductsand valves formed of a rotating force fit hub mounted on the cam shaftof the engine and slidably joumaled within the bearing tube of theshaft.

Full details of the present invention follow herein and are shown in theaccompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS In the drawings:

FIG. I shows a section through a first engine cylinder in a verticalplane B-B;

FIG. 2 shows a section through an engine block in a horizontal plane AAA FIG. 3 illustrates a section through a first engine cylinder in avertical plane CC FIG. 4 illustrates a section through a second enginecylinder in a vertical plane C C FIG. 5 shows a section through a thirdengine cylinder in a vertical plane C C FIG. 6 shows a section through afourth engine cylinder in a vertical plane C -C and FIG. 7 illustratesthe diagram of the engine working cycle.

DESCRIPTION OF INVENTION The present invention is described inconnection with a conventional four-stroke spark ignited engine normallysupercharged by the delivery of air from a chamber below the piston tothe working chamber above the piston. Such enginges are well known andare therefore, not described herein in great detail.

Referring now more particularly to FIGS. 1 and 2, it should beunderstood that the illustrated and described example is a four-cylinderspark-ignition engine which is otherwise of conventional design. Theengine head 1 comprises ducts for each of said cylinders in which arelocated a suction valve 2 and an exhaust valve3 controlled by a camshaft 4 rotatably joumaled in a tubular extension 4a running the lengthof the cylinder block 5. The cylinders have a differential internalborings d and d in which there is mounted a correspondingly shapedpiston 6 having a head 6a which forms beneath it an annular workingchamber or space 7 as well as the chamber above the piston head. Intothe annular space 7 below the piston, there is drawn additional airthrough an inlet opening 8, either from the crankcase or the atmosphere.The additional air is compressed in this annular space 7 on thedownstroke of the piston, indicated by the arrow P. The sequence of theindividual cylinders is indicated in FIG. 2 by numbers I, II, III, andIV, and the same numbers are also used in FIG. 3 through 6 illustratingthe corresponding positions of the communication holes in crank shaft 4between the inlet 8 and the annular space 7 by which the distribution ofadditional air into individual cylinders is effected.

For this distribution each of the cylinders are provided with ducts 9having lower branches 9 which open into annular spaces 7 under theassociated piston, and upper branches 9 of which open into the cylinderspace above the piston when it is in its bottommost dead centerposition. Into each of the annular spaces 7 there opens also a duct 10axially offset from duct 9. As seen in FIGS. 3 through 6, the duct 10 isalternately connected by a system of three radial communication ductsl1, 12, 13 arranged in a hub 14 on the cam shaft 4, which is in slidingengagement with the inner surface of the tubular extension 421. Theducts ll, 12 and I3 communicate with an axial central cavity I5, whichis blinded at each end beyond the region of the two extreme cylinders Iand IV, for example, by means of plugs 16. The cam shaft 4 into whosecavity I5 there open all three mentioned ducts 11 through 13, is causedto rotate by conventional means in the direction of the arrow R in FIG.I at half of the velocity of the engine crank shaft. The ducts l1, l2and 13 are arranged in a common plane C -C with duct 10, and at rightangles to each other along diametric lines radiating from the centralaxis of hub 14. As will be seen later, the position of each of the ductsin each of the sequential cylinders is offset radially to conform to thestroke cycle of the respective cylinder.

The face of each hub 14 is provided with two grooves 17 and 18 alignedwith the ducts 9. Groove 18 is large enough to bridge ducts 9, and 9Suction of additional air through each hole 8 into annular space 7 underthe piston is accomplished by means of the groove 17 which, afterpartial rotation of the crank shaft from the position illustrated inFIG. 1 in the direction of the arrow R, connects the hole 8 with thelower branch 9 of duct 9. Prior thereto, the compressed additional aircreated in the annular space 7 is passed into the cylinders space abovethe piston head 60, when the piston is at its lower dead center viagroove 18 which interconnects the lower and upper branches of ducts 9,as can also be seen from the position illustrated in FIG. I. To produceintensive rotation of the air compressed in this manner, and thus alsoof the entire cylinder charge, it is convenient to introduce, instead ofthe schematically indicated ducts 9, several tangential inlets over thecircumference of each cylinder into which air flows from a circularrecess or groove leading from inlet 8 and arranged in a non-illustratedinsert of the engine cylinders.

The behaviour of a four-stroke cycle with two-stage compression ofadditional air for a supercharged spark ignition engine can beunderstood from FIGS. l to 6 which illustrated the first phase of thisworking cycle related to the first cylinder I. FIGS. 1 and 3characterize the first cylinder I with piston 6 positioned at the end ofthe suction stroke, that is in its lower dead center in which the pistonhad previous compressed air in the annular space 7 and now superchargesits own cylinder above the piston head with compressed air.Supercharging is made possible by the illustrated position of cam shaft4, as seen in FIG. 1. Here, the groove 18 which is arranged with groove17 in the hub 14 in in the same plane B-B, permits the indicatedconnection of both branches 9 and 9 of the duct 9. Bypassing of thepreviously sucked in and compressed air from the annular space 7 intothe upper space of first cylinder I is thus effected. At this momentsuction inlet hole 8 for drawing in additional air is closed fromcommunication with duct 9 and connecting duct is also blocked, as can beseen from FIG. 2, cp. first cylinder 1, and from FIG. 3.

If, simultaneously, the ignition sequence comprises serially cylindersl-III-IV-II, as in the given case, then in fourth cylinder IV piston 6is in a phase at the end of its expansion stroke, that is in the samelower dead center position as the piston in first cylinder I. However,since the cam shaft rotates at half the speed of the engine crank shaft,the group of three communication ducts Ill, l2, l3 bored at right angleswith respect to each other, are sequentially arranged (FIG. 3 to FIG. 6)so that in the fourth cylinder IV duct 12 communicates with duct 10,while in second cylinder II and third cylinder III, the pistons of whichare in the upper dead center, ducts I1 and 13, respectively communicatewith duct 10. Due to the fact that all of the ducts 11, I2 and I3communicate, as already mentioned, with cavity 15 of cam shaft 4, thegiven position of ducts 10, 1 11 and 13, permit additional air to passfrom the fourth cylinder IV through cavity 15 to both second cylinder IIand third cylinder III, as indicated in FIG. 2 and in FIGS. 4 and 5 byarrows Q so that fourth cylinder IV charges the annular spaces 7 of bothcylinders II and III. In the following stroke, that is while piston 6 ofcylinders II and III move into their lower dead center positions thepre-compressed air previously introduced into cylinders II and III, isfurther compressed in the respective annular spaces 7 of the cylindersII and III, thus giving rise to the two stage compression of air in therespective lower chambers 7.

The described working cycle connected with cylinder I can also beunderstood from the working diagram in FIG. 7 in which there isgraphically illustrated all four working phases of the cylinders I, II,III and IV, showing the mutual relationship of the fuel and additionalair pressure cycles. The vertical coordinates of the graph are graduatedin degrees of rotation of the crank shaft, the horizontal coordinatedenotes pressure, from a base of one atmosphere. The curves drawn infull lines indicate fuel pressure in the individual cylinders, and thecurves drawn in dashed lines illustrate the corresponding pressurecurves of additional air in the lower chambers of spaces 7.

Following the upper section of the graph, the pressure curves ofcylinder I which is effected during two rotations of the crank shaft andone rotation of the cam shaft 4, shows a similar pattern as the workingcurve of a conventional four stroke engine. The effect of thesupercharging, of the present invention is omitted from this curve. From0 to 180 the piston is in its downstroke and the cylinder is in itssuction phase S, from 180 to the cylinder is placed under compression Kas the piston rises at the end of which occurs ignition Z; from 360 to540 the cylinder is under expansion E, and from 540 to 720 the cylinderis under exhaustion V. The dashed line illustrates the parallel pressurecurve of the additional air flow created in the lower chamber. At 180and 540 the lower chamber achieves maximum air compression k which ismade use of in section A, for super-charging cylinder I via its own duct9 and in section B, for charging the annular lower chambers of cylindersII and III via duct 10. The pistons in cylinders II and III are in theupper dead center position at this time. Charging of these twoassociated cylinders is accomplished by passing the pre-compressed airfrom cylinder IV in which, as already explained above, expansion E isterminated (see also FIG. 2) via duct 10 and channels 15 in thedirection of the indicated arrows Q. The air in the lower chamberthereafter expands as seen by e and in this latter period a small amountof air is diverted as will be seen into the working cylinders above thepiston to oxidize residual fuel components. The described workingprocess is repeated in each cylinder cyclically, by rotating the crankshaft through 180 which can be read from the diagram, taking intoaccount the sequence of ignition I-IIIlV-II of the indivdiual cylinders.The subscripts 2, 3 and 4 are used to denote the time sequence for therespective cylinders.

It is, therefore, obvious from this diagram that if for example,cylinder III charges itself via duct 9 in that part of section A; fromits own annular space 7, the annular space 7 of cylinder II in whichexpansion takes place supplies precompressed air into the annular spaces7 of cylinders I and IV the pistons of which are then in the upper deadcenter. Expressed generally, each cylinder has two stages of compressioncorresponding to the portion of its cycle during which its piston is inits lowermost dead center. In the first stage, corresponding to thesuction phase of the cylinder, the cylinder charges itself, via duct 9and the second stage corresponding to the expansion phase of thecylinder, the cylinder charges, via duct 10, the two other cylinders inwhich the pistons are in their uppermost dead center (compression andexhaust phases) respectively. Only at the end of the expansion strokedoes air enter the cylinder. Since at all times in the cycle, two of thecylinders have their pistons in the down position, that is during thesuction and expansion phases, they act sequentially to supply itself andthe others with compressed air. In the pictured example, cylinders I andIV are those simultaneously compressing air in their annular spaces,cylinder I being in its first stage compression, in which it chargesitself, while cylinder IV has passed the first stage and is in thesecond stage, charging the two remaining cylinders II and III via duct10. The second stage of cylinder IV is, of course, simultaneous withfirst stage of cylinder I.

The sequence of operation is such that during the upward movement of thepiston 6 as during the exhaust stroke of the given cylinder air iscaused to be sucked into the annular space 7 via the groove 17 frominlet 8. On the subsequent down stroke, air is compressed in the annularcylinder, passing out via duct 9 to charge itself, on the next upwardstroke, both ducts 9 are blocked, but additional air is supplied viaduct 10 from the second stage compression of one of the other cylinders,and lastly on the remaining downward stroke compressed air is deliveredvia duct 10 to the other cylinders.

For the purpose of the additional oxidation of combustion products so asto obtain their effective neutralization directly in the cylinder, therequired amount of compressed air is introduced toward the end of theexpansion stroke, in this phase into the cylinder from cavity of camshaft 4 through duct 19 in the cam shaft joining duct 20 in the cylinderblock 5. This duct 20, together with duct 19, is arranged in stillanother plane than the plane of holes Ill, 12 and 13, and the plane ofgrooves 17 and 18, see FIGS. 2 and 6.

It is also possible to draw compressed air from the annular spaces ofthe cylinders and to introduce this air after the exhaust valve opens inorder to obtain the same purpsoe of neutralization of exhaust gases inthe exhaust portion. In addition, it is possible by throttling thesucked air introduced into the annular space 7 through passage ducts 8,to regulate the degree of supercharging, and thus also, for practicalpurposes, to change the compression ratio of the engine.

In comparison with theknown principle the characteristic novel featureof the invention resides in the fact that the invention uses an entirelydifferent distribution of the additional air which is compressed in twostages which results in a more pronounced or double effect ofsupercharging the engine, the power of which is also correspondinglyincreased.

It is obvious to those skilled in the art that the described andillustrated method of this two-stage compression of additional air forsupercharging a fourstroke spark-ignition engine may be used with thesame advantages in multicylinder combustion engines, or incompression-ignition engines, with valve control of the OHV and OHCtypes, without exceeding the scope of this patent. Thus, the presentdisclosure is to be taken as illustrative only.

What is claimed is:

l. A method of supercharging a four stroke internal combustion enginehaving a plurality of sequentially operable cylinders and pistons eachcylinder being divided by its piston to have an upper and lower chamber,each of said pistons being cyclically operated with two upstroke and twodownstroke movements comprising the steps of admitting air into thelower chamber of each cylinder on one upstroke of its-associated pistonfrom outside the engine and on the second upstroke of said piston froman associated cylinder having its piston in a downstroke and dischargingcompressed air from said lower chamber on one downstroke of itsassociated piston to the lower chamber of an associated cylinder havingits piston on the upstroke and on the other down stroke to the upperchamber of its own cylinder whereby air is admitted at least twice tothe lower chamber for compression and discharged in part to anassociated cylinder on one downstroke and in remainder to the upperchamber of its own cylinder on the succeeding downstroke whereby the airdischarged to charge its own cylinder is compressed in two stages withinsaid cylinder.

2. Apparatus for supercharging an internal combustion engine having ablock, a plurality of cylinder located within said block, each of saidcylinders having a differential piston movable twice between an upstrokeand a downstroke in a four-stroke cycle, and forming an upper and lowerchamber in said cylinder and valve means associated with each of saidcylinders and interconnected with each other for flow of airtherebetween, said valve means being synchronously operable inconjunction with the cycle of said pistons to admit air into the lowerchamber of each cylinder during the upstroke of its piston and todischarge air from said lower chamber during the downstroke of itspiston, said valve means including means for discharging a portion ofsaid air from each cylinder during one .downstroke to the lower chamberof an associated cylinder in which the piston of the associated cylinderis in one upstroke, and for causing the lower chamber of each cylinderto receive compressed air from at least one associated cylinder whosepiston is in the other downstroke during the other upstroke of thepiston of each cylinder, each cylinder compression during the otherdownstroke the air remaining in its lower chamber after the onedownstroke and the compressed air received from the associated cylinderduring the one upstroke and thereafter discharging the same into theupper chamber of each said cylinder.

3. The apparatus according to claim 2 including means for admitting airto said lower chamber from without said engine during said one upwardstroke of said piston.

4. The apparatus according to claim 2 wherein said valve means comprisesa pair of first duct means extending through said block in a commonplane parallel to the axis of its associated cylinder, one of said pairof ducts being located below and the other of said pair of ducts beinglocated above the associated piston when said associated piston issituated in the downstroke position, and second duct means offset fromthe plane of said first duct means and extending through said blockbelow its associated piston when said associated piston is situated inits downstroke position, a shaft journaled within said block androtatable about its horizontal axis in synchronism with the pistons,said shaft extending transversely to said cylinders, said block havingan air inlet port associated with each of said cylinders, said shafthaving an axial bore closed at each end, a hub formed on said shaft inassociation with each of said respective cylinders, each of said hubshaving a first and second groove spaced radially about theircircumference in a plane common to the plane of said first pair of ductsand at least one radial channel in the plane of said second ductcommunicating with said axial bore, said grooves and channels beingangularly offset with respect to the axis of rotation of said shaft,said first grooves and channel being arranged so that on rotation ofsaid shaft said inlet and said one of said pair of ducts are connectedduring one upstroke of said piston, said one of said pair of ducts isconnected to said other of said pair of ducts during one of thedownstrokes of said piston, and said second duct and said channel areconnected, during the other of said downstrokes of said piston.

5. The apparatus according to claim 4 including a second channel in saidhub arranged to connect with said second duct during the otherdownstroke.

6. The apparatus according to claim 4 wherein said one downward strokeof said piston corresponds to the expansion stroke of said working cycleand the other downward stroke to the suction stroke, the upward strokescorresponding to the exhaust and compression strokes respectively.

7. The apparatus according to claim 6 including a fourth duct formed insaid block extending into the upper chamber and a corresponding channelradially formed in said hub and communicating with said axial bore, saidfourth duct and said corresponding channel being offset from said otherducts and radially arranged so that compressed air is discharged intosaid upper chamber during the end of the expansion stroke, saidcompressed air facilitating oxidation of the combustion productstherein.

1. A method of supercharging a four stroke internal combustion enginehaving a plurality of sequentially operable cylinders and pistons eachcylinder being divided by its piston to have an upper and lower chamber,each of said pistons being cyclically operated with two upstroke and twodownstroke movements comprising the steps of admitting air into thelower chamber of each cylinder on one upstroke of its associated pistonfrom outside the engine and on the second upstroke of said piston froman associated cylinder having its piston in a downstroke and dischargingcompressed air from said lower chamber on one downstroke of itsassociated piston to the Lower chamber of an associated cylinder havingits piston on the upstroke and on the other down stroke to the upperchamber of its own cylinder whereby air is admitted at least twice tothe lower chamber for compression and discharged in part to anassociated cylinder on one downstroke and in remainder to the upperchamber of its own cylinder on the succeeding downstroke whereby the airdischarged to charge its own cylinder is compressed in two stages withinsaid cylinder.
 2. Apparatus for supercharging an internal combustionengine having a block, a plurality of cylinder located within saidblock, each of said cylinders having a differential piston movable twicebetween an upstroke and a downstroke in a four-stroke cycle, and formingan upper and lower chamber in said cylinder and valve means associatedwith each of said cylinders and interconnected with each other for flowof air therebetween, said valve means being synchronously operable inconjunction with the cycle of said pistons to admit air into the lowerchamber of each cylinder during the upstroke of its piston and todischarge air from said lower chamber during the downstroke of itspiston, said valve means including means for discharging a portion ofsaid air from each cylinder during one downstroke to the lower chamberof an associated cylinder in which the piston of the associated cylinderis in one upstroke, and for causing the lower chamber of each cylinderto receive compressed air from at least one associated cylinder whosepiston is in the other downstroke during the other upstroke of thepiston of each cylinder, each cylinder compression during the otherdownstroke the air remaining in its lower chamber after the onedownstroke and the compressed air received from the associated cylinderduring the one upstroke and thereafter discharging the same into theupper chamber of each said cylinder.
 3. The apparatus according to claim2 including means for admitting air to said lower chamber from withoutsaid engine during said one upward stroke of said piston.
 4. Theapparatus according to claim 2 wherein said valve means comprises a pairof first duct means extending through said block in a common planeparallel to the axis of its associated cylinder, one of said pair ofducts being located below and the other of said pair of ducts beinglocated above the associated piston when said associated piston issituated in the downstroke position, and second duct means offset fromthe plane of said first duct means and extending through said blockbelow its associated piston when said associated piston is situated inits downstroke position, a shaft journaled within said block androtatable about its horizontal axis in synchronism with the pistons,said shaft extending transversely to said cylinders, said block havingan air inlet port associated with each of said cylinders, said shafthaving an axial bore closed at each end, a hub formed on said shaft inassociation with each of said respective cylinders, each of said hubshaving a first and second groove spaced radially about theircircumference in a plane common to the plane of said first pair of ductsand at least one radial channel in the plane of said second ductcommunicating with said axial bore, said grooves and channels beingangularly offset with respect to the axis of rotation of said shaft,said first grooves and channel being arranged so that on rotation ofsaid shaft said inlet and said one of said pair of ducts are connectedduring one upstroke of said piston, said one of said pair of ducts isconnected to said other of said pair of ducts during one of thedownstrokes of said piston, and said second duct and said channel areconnected, during the other of said downstrokes of said piston.
 5. Theapparatus according to claim 4 including a second channel in said hubarranged to connect with said second duct during the other downstroke.6. The apparatus according to claim 4 wherein said one downward strokeof said piston Corresponds to the expansion stroke of said working cycleand the other downward stroke to the suction stroke, the upward strokescorresponding to the exhaust and compression strokes respectively. 7.The apparatus according to claim 6 including a fourth duct formed insaid block extending into the upper chamber and a corresponding channelradially formed in said hub and communicating with said axial bore, saidfourth duct and said corresponding channel being offset from said otherducts and radially arranged so that compressed air is discharged intosaid upper chamber during the end of the expansion stroke, saidcompressed air facilitating oxidation of the combustion productstherein.